A belt retractor with the above-mentioned characteristics is described in DE 103 60 032 A1. To prevent the blocking mechanism of the belt retractor triggering when the seat belt is retracted under the effect of the roller spring or braked abruptly at the end of the retraction path after the passenger has unfastened the seat belt, the familiar belt retractor already provides for a cutoff of both the webbing-sensitive and of the vehicle-sensitive control systems, so that an unwanted blocking of the belt shaft at the end of the seat belt's retraction path is prevented.
For this purposes the familiar belt retractor has a locking disc on the belt shaft and rotating with the belt shaft that controls a stationary catch lever on bearings rotatable relative to the housing by means of a guide curve formed on it that in a function range in which almost the whole of the seat belt is rolled onto the belt shaft as a direct effect on the sensor lever of the vehicle sensor that works together with the cam disc and immobilizes this and in this way switches the vehicle-sensitive control system off. Insofar as the webbing-sensitive control system is realized through a cam disc formed with appropriate inertia, to switch the webbing-sensitive control system off there is an additional lock on the belt shaft, which is coupled for its operations via a guide gate to the catch lever for switching the vehicle sensor off and engages with the cam disc in its blocking position brought about by the locking position of the catch lever and locks the cam disc torque-proof with the belt shaft.
The familiar belt retractor has the disadvantage that different levers are provided for switching off both the vehicle-sensitive and the webbing-sensitive control systems, which makes the structure of the belt retractor complicated and the construction cost is correspondingly high. In addition, the two control systems can only be switched off consecutively, because initially the operation of the catch lever for the vehicle sensor is a prerequisite for the control of the lock for the webbing-sensitive control system. Because several control procedures are necessary, a corresponding fault dependency cannot be ruled out.
In addition, it is already known from DE 100 27 134 A1 that with a belt retractor with an inert cam disc on the shaft extension the vehicle sensor is to be attached to the inside of a cover spanning the control system and the sensor lever of the vehicle sensor is to engage with the external gearing of the cam disc to control it.